Dinámica poblacional de arvenses en el cultivo del pipian (Cucurbita pepo L.) producido bajo un sistema de manejo orgánico y un sistema de manejo convencional, en Tipitapa, Masaya 2007

Actualmente, el manejo de arvenses en las Cucurbitaceae es a base de herbicidas, repercutiendo en serios problemas al ambiente y al hombr e. En la finca experimental El Plantel, ubicado en el km 43 ½ carretera Tipitapa – Masaya, se estableció un estudio con el objetivo de conocer la dinámica poblacional de arvenses y su incidencia en el cultivo de pipián Cucurbita pepo L; producido bajo dos sistemas de manejo. Se evaluó un sistema convencional con el uso de Completo (12 - 30 - 10) 522.98 Kg/Ha, Urea 190.06 Kg/Ha, y un sistema orgánico con el uso Humus 10,886.95Kg/Ha, Compost: 21,900.62Kg/Ha, Biofertilizante: 14,765.21 Kg/Ha En una área 525m2, en tres parcelas de 80.5 m2, alternando con el pipián, el caupí. ( Vigna unguiculata . (L) Walp). En la diversidad se encontraron 13 especies en el sistema orgánico, predominando Tithonia rotundifolia (Mill) Blake, Boerhavia erecta L., Sorghum halepense (L) P e rs. Y 10 familias, entre ellas, Portulacaceae, Asteraceae, Nyctaginaceae, y Cyperaceae. Y en el sistema convencional 11 especies, predominando, Ixophorus unicetus (Presl), Sorghum halepense (L) P ers, Tithonia rotundifolia (Mill) Blake, y 9 familias, sobres alieron Poaceae, Portulacaceae, Asteraceae, y Nyctaginaceae. El porcentaje de cobertura en los dos sistemas de manejo se presento similar. La biomasa por familia, especie y cultivo, fue mayor en el sistema orgánico. El rendimiento del cultivo no reflejo di ferencia significativa entre los dos sistemas de manejo evaluados. Los resultados demostraron que presencia de arvenses no afectó el desarrollo y crecimiento del cultivo. El manejo orgánico puede verse como una alternativa viable para el productor y para l a conservación del ambiente, a pesar de ser este un corto ciclo, este manejo muestra que a futuro se pueden obtenerse mejores resultados

Dinämica poblacional de arvenses en el cultivo de la yuca (Manihot esculenta, Crantz) bajo un sistema convencional y un sistema orgánico

En Nicaragua el cultivo de yuca ( Manihot esculenta Crantz), se siembra tradicionalmente en suelos de baja fertilidad y las arvenses representan el 30% o más del costo de producción. Se evaluó la Dinámica poblacional de arvenses en el cultivo de la yuca, bajo dos sistemas de manejo convencional y orgánico. En la finca El Plantel km 43 1/2 carretera Tipitapa- Masaya, en el 2007 – 2008. Se establecido un diseño no experimental con dos tratamientos: un sistema de manejo convencional el uso de abono completo 12 – 24 – 12 y Urea 46 %- y uno sistema orgánico el uso de lombriz Humus, compost y biofertilizante. En ambos sistemas se encontró una diversidad de 15 especies de arvenses distribuidas en 10 familias. En el Sistema Orgánico predominaron especies de la clase dicotiledóneas, Jalacate Tithonia rotundifolia L. (jalacate), Golondrina ( Boerhravia erecta L) . Desmodium tortuosum (S.W) D.C, (pega pega), Portulaca oleraceae L, (Verdolaga) y las monocotiledoneas, Invasor ( Sorghum halepense (L.)) y Coyolillo ( Cyperus rotundus L), y el Sistema Convencional con menor presencia de especies. En el banco de semilla las clases dicotiledóneas y monocotiledonea, predominan en el sistema orgánico. La biomasa en ambos sistemas, acumularon mayor peso las familias Poaceae, Asteraceae, Cyperaceae y las Papilionaceas. Con relación a peso acumulado por especie, en el sistema orgánico el mayor peso se encontró en, Jalacate ( Tithonia rotundifolia (Mill) Blake), e Invasor ( Sorghum halepense (L) Pers) y en el sistema convencional, Zacate dulce ( Ixophorus unicetus (Persl)) e Invasor ( Sorghum halepense (L) Perl). La cobertura decreció a medida que el cultivo cerraba su ciclo. En los dos sistemas de manejo, el número promedio de raíces por planta, diámetro de raíz y rendimientos promedio de yuca, no presentaron diferencia significativa. Caso contrario con la longitud de la raíz. El sistema de manejo orgánico puede verse como una alternativa viable para el manejo del cultivo de yuca, donde los resultados fueron más satisfactorios

Dinámica poblacional de arvenses en el cultivo de maiz (Zea mays L.) variedad NB-6 bajo los sistemas orgánico y convencional en la finca El Plantel, Tipitapa, Masaya, 2009

Las arvenses, tanto anuales como perennes, son un problema mundial en el cultivo del maíz. El crecimiento descontrolado de las malezas puede provocar grandes pérdidas de rendimiento de este cultivo. El estudio se realizó en finca experimental El Plantel de la Universidad Nacional Agraria, ubicada en el kilómetro 43 ½ carretera Tipitapa – Masaya, municipio de Masaya, de marzo a agosto 2009. Se evaluó el comportamiento de las arvenses en el cultivo de maíz, variedad NB-6, manejado bajo dos sistemas de producción: orgánico y convencional, se consideraron como dos tratamientos, establecidos en cuatro pseudorrepeticiones. El área experimental fue de 672 m2. La distancia entre pseudorrepeticiones 1 m. Las variables evaluadas fueron: diversidad, abundancia, biomasa y cobertura de arvenses y en el cultivo rendimiento en kg/ha. El predominio de las arvenses en el cultivo bajo los dos tratamientos fue similar. Se identificaron 11familias representadas por 21 especies. De éstas, 19 en el sistema orgánico y 17 en el sistema convencional. De las 21 especies, 15 pertenecen a la clase dicotiledóneas, éstas predominaron en el sistema orgánico: Cleome viscosa L. (Frijolillo de playa), Sida acuta Burn. F (Escoba lisa) y Portulaca oleracea L. (Verdolaga) de las familias Cappari daceae, Malvaceae y Portulacaceae. Las monocotiledóneas fueron Poaceae y Cyperaceae, predominando la especie: Ixophorus unicetus Presl. ( Zacate dulce). En el sistema convencional las familia Cyperaceae y Capparidaceae, en ellas predominaron las especies Cyperus rotundus L. (Coyolillo) y Cleome viscosa (L) respectivamente. La cobertura decreció en ambos sistemas a medida que el cultivo cerraba su ciclo, mostrando comportamiento similar en ambos tratamientos. La biomasa fue mayor el sistema orgánico (6,368 g/m2) con respecto a la biomasa en el sistema convencional (5,011.1 g/m2). La familia Poaceae obtuvo mayor biomasa (3205.5 g/m2) en el sistema orgánico, a diferencia del sistema convencional. (1765.4 g/m2). En el rendimiento no hubo diferencias estadísticas significativas en ambos sistemas de manejo donde (P=0.97).

嵩草属植物的系统学研究

嵩草属隶属于莎草科苔草亚科苔草族，主要分布于北半球温带地区，少数种类为环北极分布，有一种产于泰国清迈，一种产于苏门达腊岛北部高山。本‘文在形态学、微形态学、解剖学和胚胎学研究的基础上，对嵩草属植物进行了全面的分类学修订，根据属内各类群之间的系统演化关系建立了一个新的属下分类系统，确认了世界范围内53种3亚种嵩草属植物，并做出5个种上等级的新组合，描述了一个新亚组。 作者研究了国内外14家标本馆（室）的3000多份腊叶标本并进行多次野外的实地观察，对嵩草属植物的形态学性状进行了详细的比较和分析，评价了它们的系统学价值及其演化趋势。在嵩草属中，花序是由小穗排列成的圆锥花序或穗状花序，花序各部分的形态性状是种及种上等级分类的基础;花序的演化趋势是由圆锥花序到穗状花序，小穗是从由数朵雄花与1朵雌花组成简化到由1朵雌花组成。但是，花序和小穗由复杂到简单的进化在嵩草属中平行地发生于不同的类群中。先出叶的性状状态是分种的主要特征之一，通常认为边缘开裂的先出叶是原始的，边缘合生而为囊状的先出叶是进化的。同样，先出叶由开裂到合生的进化也是多次发生的。此外，根状茎、秆、叶鞘、叶片、柱头及小坚果等的性状状态对于种及种上等级的分类都具有重要的意义。 应用扫描电子显微镜对38种（或亚种）嵩草属植物的小坚果表面进行了观察，证明小坚果纹饰在种及种上等级的分类中具有重要的参考价值，并能揭示种及种下等级的亲缘关系。例如，分布于喜马拉雅东部至横断山地区的3种植物，K．clarkeana、K．curvata和K．fragilis外部形态非常相似，难于区分，而其小坚果的微形态特征却可以提供3种之间关系的证据。K．clarkeana与K．fragilis果实表面的特征完全一致，且与其它植物有显著区别，应为同种植物;K．curvata与它们明显不同，也与其它种有较大差异，应为独立的种。K．gramini folia，K．cercostach ys和K. nepalensis果实表面纹饰具有一些共同的特征，说明它们之间的亲缘关系较近。K．filicina和K．duthiei也存在同样的情形。 通过对秆和叶片的横切面和表皮的解剖学观察比较，发现嵩草属植物秆的横切面表现出由三角形到圆形的一系列变化。秆的横切面明显地分两个区域，中部的髓由较大而无色的细胞组成，其中心常碎裂形成大的气腔;外围的绿色部分，由绿色组织及分布其中的气腔和外韧维管束及与其相伴的厚壁组织组成。秆的表皮与叶片下表皮非常相象。叶片横切面的外形为V形、新月形或半圆形。V形的叶片具有明显发育的中脉并且在远轴面凸起，形成脊;新月形和半圆形的叶片中脉发育不明显，也无脊。叶片的表皮细胞均为长方形，垂周壁波纹状;平列型的气孔器纵向成行排列，多局限于下表皮;上表皮近边缘及脉附近的细胞常常在细胞的一端形成乳突。秆和叶片横切面的形态对于分种及种上等级的划分具有参考价值。 胚胎学研究表明小孢子、胚囊和胚的发育与莎草科其它类群一致。花粉为假单体花粉( pseudomonad)，成熟花粉三核。胚珠倒生，厚珠心，双层珠被，珠孑L由内珠被形成。胚囊的发育为蓼型，原胚的发育为柳叶菜型灯芯草变型。首次观察到，在大孢子四分体时期，合点端和珠孔端两个大孢子细胞开始时体积都增大，而中部两个很快退化，稍后珠孔端一个也退化，合点端一个为功能大孢子，发育成为胚囊。根据胚胎学证据，不支持将嵩草属与苔草族一起另立为嵩草科。 嵩草属中较原始的一个亚属subg. Compositae主要分布于西喜马拉雅至横断山地区，还有一种见于泰国，一种产于苏门达腊，而后2种植物还具有一些最原始的形态性状。结合地史的变化推测，嵩草属可能在第三纪早期起源于古地中海的东部和北部。 根据形态学和解剖学性状的分析表明，许多性状在嵩草属中是平行演化的，如花序和小穗由复杂到简单、秆由圆柱形到三棱形、叶片横切面由V形到半圆形等。该属的属下分类应该追溯这些平行的演化线，而不能像以前的分类那样，将它们横向地划分为几个组或亚属。作者认为嵩草属有3个大的进化分支，据此将其划分为3个亚属。Subg. Compositae，12种，是较原始的一个分支。叶近基生，叶片扁平;花序多疏松圆锥状，少穗状，苞片多为叶状;小穗两性到单性，先出叶多为囊状，少边缘分离，退化小穗轴明显、扁平、较长。Subg. Blysmocarex，仅2种，是较早分化而相对隔离的一个分支。根状茎匍匐状;花序由圆锥状到穗状，小穗两性或单性;柱头2。Subg. Kobresia，种类最多。叶片扁平或内卷;秆三棱形到圆柱形;花序紧密，复杂到简单，苞片不为叶状;小穗两性或单性，先出叶由开裂到合生，退化小穗轴较小而不显著。根据该亚属呈现出的不同的性状演化系列，可以分为3个组。Sect. Kobresia花序圆锥状至穗状，小穗多为两性，少为单性，先出叶边缘分离。含3个亚组：subsect. Kobresia，8种2亚种．植株纤细，秆与叶均为丝状;subsect. Royleanae，8种l亚种，植株较粗壮，叶片扁平或对折;subsect. Sibiri-cae，4种，秆较粗，叶片内卷。Sect. Psmmostachys，仅2种，小穗两性，先出叶完全合生为囊状。Sect．Hemicarex花序一般为穗状，稀圆锥状，小穗多为单性，少两性。分为四个亚组：subsect. Forexeta，6种，叶片内卷或对折，先出叶线形，边缘分离或合生;subsect. Chlorostachys，3种，叶片扁平，小穗两性;subsect. Holmia，4种，叶片扁平，小穗单性;subsect．Utriculatae，5种，叶片丝状，先出叶完全合生为囊状，不为线形。嵩草属的属下分类纲要如下： Subgenus 1. Compositae (Clarke) Kukkonen Type: K. laxa Nees. Subgenus 2. Blysmocarex (Ivanova) S. R. Zhang Type: K. macrantha Boeck. Subgenus 3. Kobresia Section 1. Kobresia Subsection 1. Kobresia Type: K. simpliciuscula (Wahl. ) Mack. Subsection 2. Royleanae (Ivanova) S. R. Zhang Type: K. royleana (Nees) Boeck. Subsection 3. Sibiricae (Ivanova) Egorova Type: K. sibirica (Turcz. ex Ledeb. ) Boeck. Section 2. Psmmostachys Ivanova Type: K. robusta Maxim. Section 3. Hemicarex (Bentham) Clarke Subsection 4. Forexeta (Raffin. ) S. R. Zhang Type: K. cercostachys (Franch. ) C. B. Clarke. Subsection 5. Chlorostachys (Ivanova) S. R. Zhang Type: K. duthiei C B. Clarke. Subsection 6. Holmia (Boern. ) S. R. Zhang Type: K. esenbeckii (Kunth) Noltie. Subsection 7. Utriculatae S. R. Zhang Type: K. prainii Kukenthal.

中国东北样带孢粉-植被的定量关系及古生物群区的反演

基于中国东北样带（NECT）30个植被样方调查和表土孢粉资料，从个体、群落水平研究了孢粉－植被关系，结果表明，孢粉类型与植被关系密切，在 ＝ 0．05的显著性水平上，相关系数大于0．5;表土孢粉组合与植物群落间有较大的相似性，相似系数大于50％。采用定量描述花粉与植物关系的参数：联合指数（association）A、超代表性指数（over-representation）O、低代表性指数（under-representation）U、相关系数（correlation coefficient）C和代表性系数（representation coefficient）R等值，应用TWINSPAN分类、PCA排序和回归分析，把表土花粉类型划分为4类：具代表性类群组Group1，它们能正确反映植被;超代表性类群组Group2，它们常具有高花粉值与植被不成比例;低代表性类群组Group3，它们的花粉很难分离提取;以及低代表性类群的Group4，其花粉在土壤地层中较常见;指出一些常见花粉类型：松（Pinus）、桦（Betula）、栎（Quercus）、椴（Tilia）、槭（Acer）、榆（Ulmus）、蒿（Artemisia）、藜（Chenopodiaceae）、禾本科（Gramineae）和莎草科（Cyperaceae）的回归参数在东部森林区和西部草原区是有变化的，因此回归参数在应用于古植被恢复中要注意适用范围。 以Biomization模型为基础，根据植物的生理生态特性，定义了NECT孢粉类型的植物功能型（PETs）各种生物群区（Biome）的PFTs组合，构建了经表土孢粉检验的适用于NECT的以孢粉数据为驱动的模型框架，该模型模拟的生物群区与其化指标（气候、植物生理、土壤等）模拟划分的BIOME（Holdrige, BIOME3）是可比的，与植被类型有较好的对应性。 根据29剖面（986个样品）的孢粉数据，重建了NECT 6 kaB.P以来的生物群区。从时空二方面阐述了NECT6kaB.P以来生物群区的分布特点： （1）6ka B. P是一暖湿期，气温比现在高1～4℃，降水比现在多50％。落叶阔叶林分最广，面积最大。森林草原、落叶阔叶林、针阔混交林向西延伸最远。 （2）5ka B. P 是一降温期，气温比现在低2℃，降水多30％。有苔原、寒温带针叶林分布。 （3）4ka B. P是一暖湿期，气温比现在高1～2℃，降水比现在多50％。针阔光林和森林草原有最大分布面积。 （4）3Ka－2kaBP的气温与现代相似，降水比现在多20％左右。与4Ka B. P相比，森林和森林草原过渡带都向东移动。 （5）1Ka B. P的气温与现代相似，降水比现在多10％左右。草原向东大幅度扩张，森林分布面积减小。 （6）东部森林，中部森林草原，西部草原的分布格局的3Ka B. P基本确定，此后随着气候的不断变干冷，草原向东扩张。 （7）森林向扩张最大距离的时期发生在6Ka B. P，此时也是森林草原向西扩张最远时期。落叶阔叶林、针阔混交林、森林草原向西移动最大距离的时间是6Ka B. P，草原向西移动最远距离的时期发生在3Ka B. P。

青藏高原矮嵩草草甸种子库的初步研究

The seed bank of Kobresia humilis meadow in Qing- Zang Plateau was preliminaryly studied and the relationships among seed bank , seed rain and above-ground vegetation were compared and analysed.The results showed that there were 23 species in the seed bank in both of green up and withering stage. In species composition of the seed bank ,Ranunculaceae and Leguminosae were dominant ,while the percentage of Cyperaceae and Gramineae were lower. The percentage of K. humilis seeds was relatively lower with 0. 97 % in green up stage and 1. 97 % in withering stage. The species composition of the seed bank correlated with that of the seed rain ( r = 0. 7505 , P < 0. 01) ,and there were 18 common species which was 78. 3 %of species of the seed bank. Only 41. 81 %of above-ground vegetation species presented in the seed bank. The seed numbers of the dominant plant species in vegetation were smaller , with lower percentage in the seed bank. Therefore , the dominant vegetation of K. humilis et al. mainly depended on vegetative reproduction to maintain and strengthen. From vegetation to the seed bank in green up stage ,the species diversity decreased by 9. 94 %. It implied that the seed bank was the source of vegetation regeneration , but also a mechanism of preserving species diversity of the plants.

Status and dynamics of Kobresia pygmaea ecosystem on the Tibetan plateau

This paper provides information about the distribution, structure, and ecology of the world's largest alpine ecosystem, the Kobresia pygmaea pastures in the southeastern Tibetan plateau. The environmental importance of these Cyperaceae mats derives from the extremely firm turf, which protects large surfaces against erosion, including the headwaters of the Huang He, Yangtze, Mekong, Salween, and Brahmaputra. The emphasis of the present article is on the climate-driven evolution and recent dynamics of these mats under the grazing impact of small mammals and livestock. Considering pedological analyses, radiocarbon datings, and results from exclosure experiments, we hypothesize that the majority of K. pygmaea mats are human-induced and replace forests, scrub, and taller grasslands. At present, the carrying capacity is increasingly exceeded, and reinforced settlement of nomads threatens this ecosystem especially in its drier part, where small mammals become strong competitors with livestock and the removal of the turf is irreversible. Examples of rehabilitation measures are given.

中国北方草本植物及表土有机质碳同位素组成

Recently, more and more attention has been paid to stable isotope ratios in terrestrial depositional systems. Among them, δ~(13)C value is mainly determined by the surface vegetation, while vegetation is directly related to climate, therefore, carbon isotope ratio in soil organic matter and pedogenic carbonate has been employed as an important paleoecological indicator. In order to test the paleoecological information extracted from stable isotope ratios in terrestrial depositional systems, it is necessary to study the relationships between δ~(13)C value in standing terrestrial plants and today climate, as well as between δ~(13)C value in modern surface soil organic matter and standing vegetation. Thus, these relationships were studied in this paper by means of analysing δ~(13)C in standing plants and modem surface soil organic matter in North China. The main results and conclusions are presented as following: 1. According to their δ~(13)C values, 40 C-4 species represent about 16% of the 257 plant species sarnpled from the North China. C-4 photosynthesis mainly occurs in Poaceae, Cyperaceae and Chenopidaceae families, and percentage representation of C-4 photosynthesis is up to 56% in Poaceae family. 2. The δ~(13)C values of C-3 plant species in North China vary from -21.7‰ to -32.0‰ with an average of -27.1‰, and 93% focus on the range of -24.0‰ ～ -30.0‰; δ~(13)C values of C-4 plant species in North China are between -10.0‰ ～ -15.5‰ with an average of -12.9‰, and 90% concentrate on the range of -11.0‰ ～ -15.0‰. 3. The δ~(13)C composition of C-3 plant species collected from Beijing, a semi-moist district, mainly vary between -27.0‰ ～ -30.0‰, and the average is -28.7‰; the δ ~(13)C values of plants in the semi-arid district, east and west to the Liu Pan Moutain, focus on the range of-26.0‰ ～ -29.0‰ and -25.0‰ ～ -28.0‰, respectively, with the mean value of -27.6‰ and -26.6‰, respectively; the δ~(13)C composition in the arid district dominantly vary from -24.0‰ to -29.0‰, with the average of -26.2‰, and among them, the δ~(13)C values of C-3 plant species in deserts are often between - 22‰ ～ -24‰; the δ~(13)C values in the cold mountain district concentrate on the range of -24.0‰ to -29.0‰, with the average of -26.3‰. 4. The main range of δ~(13)C composition of C-4 plant species, derived from Beijing, a semi-moist district, are -13.0‰ ～ -15.5‰; the semi-arid district, -11.0‰ ～ -14.0‰; the arid district, -11.0‰ ～ -14.0‰. The mean values of them are -14.0‰, -12.4‰,-12.7‰, respectively. 5. From east to west in North China, δ~(13)C values of C-3 plant species increase with longitude. The correlation between δ~(13)C ratios of C-3 plant species and longitude is linear. Changing temperate and precipitation and changing atmosphere pressure are spossible explanations. 6. Almost all C-3 plant species have the trends that their δ~(13)C values gradually increase with decreasing precipitation, decreasing temperature and increasing altitude. Our results show the increases of the δ~(13)C value by 0.30 ～ 0.45‰, 0.19 ～ 0.27‰ and 1.1 ～ 1.2‰ per 100 mm, I℃ and 1000 m, respectively, for all C-3 plant species together. 7. The δ~(13)C values of all C-3 plant species together and a part of C-3 species show highly significant linear correlation with the mean annual temperature, the mean annual precipitation and the altitude, and the results suggest that they can be used as proxies of these environmental variables, while, those without highly significant correlation, may be not suitable as the proxies. 8. The extent, which of responses of δ~(13)C composition to environmental variables, is different for each C-3 plant specie. 9. The δ~(13)C variations along altitude and longitude may be non-linear for C-4 p1ant species in North China. The mean annual temperature may be not important influential factor, thus, it suggests that the δ~(13)C composition of C-4 plant species may be not suitable as the proxy of the mean annual temperature. The influences of summer temperature on δ~(13)C values are much bigger than that of annual temperature, among them, the influence of September temperature is biggest. The mean annual precipitation may be one of the dominant influential factors, and it shows a highly significant non-linear relationship with δ~(13)C values, and the result indicates that δ~(13) C composition of C-4 plant species can be employed as the proxy of the mean annual precipitation. 10. The variations of δ~(13)C ratios do not show systematic trends along longitude, latitude and altitude for modern surface soil organic in Northwest China. ll. The δ~(13)C ratios of modern surface soil organic do not exhibit systematic patterns with temperature and precipitation in Northwest China, it suggests that, unless soil organic is transferred from pure C-3 or C-4 vegetation, the δ~(13)C composition of soil organic may be not used as proxies of climatic variables. 12. The δ~(13)C values of modem surface soil organic are heavier than that of standing vegetation, and the difference ofrnean δ~(13)C between them is -2.18‰. 13. Without considering the δ~(13)C difference between vegetation and soil organic, as well as the δ~(13)C drift in various enviromnent, we may not obtain the valuable information of C-3, C-4 relative biomass in vegetation. 14. The C-4 biomass contribution in vegetation increase with decreasing latitude, increasing longitude and decreasing altitude in Northwest China. The C-4 biomass almost are zero in those regions north to 38 ° N, or west to 100°E, or above 2400 m. 15. The C-4 relative biomass in vegetation increase with growing temperature and precipitation. and, C-4 plants are rare at those regions where the mean annual temperature is less 4 ℃, or the mean annual precipitation is less 200 mm, and their biomass contribution in vegetation are almost zero. Both the mean annual temperature and the mean annual average precipitation may be the important influential factors of C-4 distribution, but the dominant factors.

中国北方典型生态区表土孢粉组合特征及其与现代植被和气候的关系

Surface pollen assemblages and their relationhips with the modern vegetation and climate provide a foundation for investigating palaeo-environment conditions by fossil pollen analysis. A promising trend of palynology is to link pollen data more closely with ecology. In this study, I summarized the characteristics of surface pollen assemblages and their quantitative relation with the vegetation and climate of the typical ecological regions in northern China, based on surface pollen analysis of 205 sites and investigating of modern vegetation and climate. The primary conclusions are as follows:The differences in surface pollen assemblages for different vegetation regions are obvious. In the forest communities, the arboreal pollen percentages are more than 30%, herbs less than 50% and shrubs less than 10%; total pollen concentrations are more than 106 grains/g. In the steppe communities, arboreal pollen percentages are generally less than 5%; herb pollen percentages are more than 90%, and Artemisia and Chenopodiaceae are dominant in the pollen assemblages; total pollen concentrations range from 103 to 106 grains/g. In the desert communities, arboreal pollen percentages are less than 5%. Although Chenopodiaceae and Artemisia still dominate the pollen assemblages, Ephedra, Tamaricaceae and Nitraria are also significant important in the pollen assemblages; total pollen concentrations are mostly less than 104grains/g. In the sub-alpine or high and cold meadow communities, arboreal pollen percentages are less than 30%. and Cyperaceae is one of the most significant-taxa in the pollen assemblages. In the shrub communities, the pollen assemblages are consistent with the zonal vegetation; shrub pollen percentages are mostly less than 20%, except for Artemisia and Hippophae rhamnoides communities.There are obvious trends for the pollen percentage ratios of Artemisia to Chenopodiaceae (A/C), Pinus to Artemisia (P/A) and arbor to non-arbor (AP/NAP) in the different ecological regions. In the temperate deciduous broad-leaved forest region, the P/A ratios are generally higher than 0.1, the A/C ratios higher than 2 and the AP/NAP ratios higher than 0.3. In the temperate steppe regions, the P/A ratios are generally less than 0.1, the A/C ratios higher than 1 and the AP/NAP ratios less than 0.1. In the temperate desert regions, the P/A ratios are generally less than 0.1, the A/C ratios less than 1, and the AP/NAP ratios less than 0.1.The study on the representation and indication of pollen to vegetation shows that Pinus, Artemisia, Betula, Chenopodiaceae, Ephedra, Selaginella sinensis etc. are over-representative in the pollen assemblages and can only indicate the regional vegetation. Some pollen types, such as Quercus, Carpinus, Picea, Abies, Elaeagus, Larix, Salix, Pterocelis, Juglans, Ulmus, Gleditsia, Cotinus, Oleaceae, Spiraea, Corylus, Ostryopsis, Vites, Tetraena, Caragana, Tamaricaceae, Zygophyllum, Nitraria, Cyperaceae, Sanguisorba etc. are under-representative in the pollen assemblages, and can indicate the plant communities well. Populus, Rosaceae, Saxifranaceae, Gramineae, Leguminosae, Compositae, Caprifoliaceae etc. can not be used as significant indicators to the plants.The study on the relation of pollen percentages with plant covers shows that Pinus pollen percentages are more than 30% where pine trees exist in the surrounding region. The Picea+Abies pollen percentages are higher than 20% where the Picea+Abies trees are dominant in the communities, but less than 5% where the parent plants are sparse or absent. Larix pollen percentages vary from 5% to 20% where the Larix trees are dominant in the communities, but less than 5% where the parent plants are sparse or absent. Betula pollen percentages are higher than 40% where the Betula trees are dominant in the communities" but less than 5% where the parent plants are sparse or absent. Quercus pollen percentages are higher than 10% where the Quercus trees are dominant in the communities, but less than 1% where the parent plants sparse or absent. Carpinus pollen percentages vary from 5% to 15% where the Carpinus trees are dominant in the communities, but less than 1% where the parent plants are sparse or absent. Populus pollen percentages are about 0-5% at pure Populus communities, but cannot be recorded easily where the Populus plants mixed with other trees in the communities. Juglans pollen accounts for 25% to 35% in the forest of Juglans mandshurica, but less than 1% where the parent plants are sparse or absent. Pterocelis pollen percentages are less than 15% where the Pterocelis trees are dominant in the communities, but cannot be recorded easily where the parent plants are sparse or absent. Ulmus pollen percentages are more than 8% at Ulmus communities, but less than 1% where the Ulmus plants mixed with other trees in the communities. Vitex pollen percentages increase along with increasing of parent plant covers, but the maximum values are less than 10 %. Caragana pollen percentages are less than 20 % where the Caragana plant are dominant in the communities, and cannot be recorded easily where the parent plants are sparse or absent. Spiraea pollen percentages are less than 16 % where the Spiraea plant are dominant in the communities, and cannot be recorded easily where the parent plants are sparse or absent.The study on the relation of surface pollen assemblages with the modern climate shows that, in the axis 1 of DCA, surface samples scores have significant correlation with the average annual precipitations, and the highest determination coefficient (R2) is 0.8 for the fitting result of the third degree polynomial functions. In the axis 2 of DCA, the samples scores have significant correlation with the average annual temperatures, average July temperatures and average January temperatures, and the determination coefficient falls in 0.13-0.29 for the fitting result of the third degree polynomial functions with the highest determination coefficient for the average July temperature.The sensitivity of the different pollen taxa to climate change shows that some pollen taxa such as Pinus, Quercus, Carpinus, Juglans, Spiraea, Oleaceae, Gramineae, Tamariaceae and Ephedra are only sensitive to the change in precipitation.

New records of interesting xenophytes in the Iberian Peninsula. V

As a continuation of previous research on the naturalization of non-native vascular plants in the Iberian Peninsula new chorological data are presented for 16 xenophytes recorded between 2010 and 2014, mostly in the provinces of Huelva and Barcelona (Spain) and in the Algarve and Estremadura (Portugal). For each taxon details about distribution, habitats occupied, previous records, degree of naturalization, etc. are provided. Lachenalia bulbifera and Cyperus albostriatus are probably reported for the first time in the wild in Europe, as are Gamochaeta filaginea, and Dysphania anthelmintica and Oenothera lindheimeri for Portugal and Spain respectively. Cosmos bipinnatus is cited as a novelty for the Algarve (Portugal). Newly reported or confirmed for the province of Huelva are: Amaranthus hypochondriacus, Epilobium brachycarpum, Nephrolepis cordifolia, Ficus microcarpa, Tamarix parviflora and Tamarix ramosissima, while Atriplex semibaccata, Chloris truncata, and Elymus elongatus subsp. ponticus are new for Barcelona. Finally, Passiflora caerulea is a novelty for both Barcelona and Huelva provinces.

Paléoécologie du Quaternaire dans la région de Wainwright en Alberta

En 2012, la Commission géologique du Canada a procédé à une série de forages dans les dépôts quaternaires de la région de Wainwright dans le centre-est de l’Alberta dans le cadre d’un projet en hydrogéologie. Les forages, qui atteignent plus de 60 m de profondeur, montrent la présence de niveaux organiques intercalés dans les unités stratigraphiques minérales, dont certains contiennent des morceaux de bois qui suggèrent la présence passée in situ d’une végétation ligneuse. La position stratigraphique des sables contenant des niveaux organiques sous le till régional (Wisconsinien supérieur) laisse penser qu’ils correspondraient à des épisodes interstadiaires, voire même de l’interglaciaire Sangamonien, des datations 14C ayant livré des âges non-finis (>43 500 ans A.A.). L’objectif principal de la présente étude était de documenter la composition du couvert végétal associé aux niveaux organiques à l’aide de l’analyse pollinique et macrofossile. Plusieurs des niveaux se sont avérés pauvres ou même stériles en grains de pollen et en macrorestes végétaux. Les assemblages polliniques sont le plus souvent dominés par des espèces herbacées (p. ex.: Cyperaceae, Artemisia sp.) et des fougères. Chez les arbres, l’épinette est l’espèce la mieux représentée mais elle montre des pourcentages polliniques relativement faibles. Les assemblages macrofossiles sont notamment caractérisés par la présence de matière ligneuse, de l’épinette et de plantes aquatiques. Plusieurs échantillons contiennent aussi des charbons de bois qui témoignent de l’incidence de feux. Les résultats des analyses paléoécologiques suggèrent que le couvert végétal contemporain du dépôt des niveaux organiques était à caractère boréal ouvert. Ces niveaux auraient donc été mis en place au cours d’un intervalle climatique plus froid que l’actuel, présumément un interstade wisconsinien plutôt qu’au cours du dernier interglaciaire (Sangamonien).

Evolutionary switch and genetic convergence on rbcL following the evolution of C4 photosynthesis.

Rubisco is responsible for the fixation of CO2 into organic compounds through photosynthesis and thus has a great agronomic importance. It is well established that this enzyme suffers from a slow catalysis, and its low specificity results into photorespiration, which is considered as an energy waste for the plant. However, natural variations exist, and some Rubisco lineages, such as in C4 plants, exhibit higher catalytic efficiencies coupled to lower specificities. These C4 kinetics could have evolved as an adaptation to the higher CO2 concentration present in C4 photosynthetic cells. In this study, using phylogenetic analyses on a large data set of C3 and C4 monocots, we showed that the rbcL gene, which encodes the large subunit of Rubisco, evolved under positive selection in independent C4 lineages. This confirms that selective pressures on Rubisco have been switched in C4 plants by the high CO2 environment prevailing in their photosynthetic cells. Eight rbcL codons evolving under positive selection in C4 clades were involved in parallel changes among the 23 independent monocot C4 lineages included in this study. These amino acids are potentially responsible for the C4 kinetics, and their identification opens new roads for human-directed Rubisco engineering. The introgression of C4-like high-efficiency Rubisco would strongly enhance C3 crop yields in the future CO2-enriched atmosphere.

Investigation on phytochemical constituents and biological potential of some traditional medicinal plants

Plants and microorganisms provide the pharmaceutical industry with some of the most important sources of components for the research of new medications This thesis involves the study of three medicinal plants belonging to three different important families viz, Cyperus rotundus (Cyperaceae), Stereospermum colais (Bignoniaceae) as well as the well known medicinal plant Zingiber officinale (Zingiberaceae) as the third. The first chapter gives an overview of biologically active natural products with special reference to antioxidant, antidiabetic, anti-inflammatory and antimicrobial molecules from terrestrial sources. Chapter 2 of the thesis deals with the isolation of phytochemical constituents of the medicinal plant Cyperus rotundus and its antioxidant and radical scavenging potential. Chapter 3 of the thesis describes the studies on the roots of Stereospermum colais, A Bignoniaceae plant belonging to the genus Stereospermum which is used extensively. Chapter 3 of the thesis describes the studies on the roots of Stereospermum colais, a Bignoniaceae plant belonging to the genus Stereospermum which is used extensively in Ayurveda. Chapter 4 describes the biological potential of rhizomes of Zingiber officinale. Ethyl acetate extract of ginger (EAG) possessed antioxidant activity as is evident from the results of various in vitro assays compared to other extracts .In conclusion, medicinal plants Cyperus rotundus and Stereospermum colais have been analysed for their phytochemical constituents. Also, the positive results obtained from biological activity studies such as antioxidant, anti-inflammatory and antimicrobial activity on the isolated compounds/extracts add on to the medicinal properties of these plants. Apart from that, ethyl acetate extract of Zingiber officinale (ginger) rhizomes has been shown to have very good biological potential including glucose lowering and adipocyte differentiation inhibitory effect.

Holocene vegetation dynamics in the northeastern Rub' al-Khali desert, Arabian Peninsula: a phytolith, pollen and carbon isotope study

The Holocene vegetation history of the Arabian Peninsula is poorly understood, with few palaeobotanical studies to date. At Awafi, Ras al-Khaimah, UAE, a 3.3 m lake sediment sequence records the vegetation development for the period 8500 cal. yr BP to similar to3000 cal. yr BP. delta(13)C isotope, pollen and phytolith analyses indicate that C3 Pooid grassland with a strong woody element existed during the early Holocene (between 8500 and 6000 cal. yr BP) and became replaced by mixed C3 and C4 grasses with a strong C4 Panicoid tall grass element between 5900 and 5400 cal. yr BP. An intense, arid event Occurred at 4100 cal. yr BP when the lake desiccated and was infilled by Aeolian sand. From 4100 cal. yr BP the vegetation was dominated by C4 Chloridoid types and Cyperaceae, suggesting an incomplete vegetation cover and Aeolian dune reactivation owing to increased regional aridity. These data outline the ecosystem dynamics and carbon cycling in response to palaeomon-soon and north-westerly variability during the Holocene. Copyright (C) 2004 John Wiley Sons, Ltd.

Characterisation of Bolivian savanna ecosystems by their modern pollen rain and implications for fossil pollen records

The majority of vegetation reconstructions from the Neotropics are derived from fossil pollen records extracted from lake sediments. However, the interpretation of these records is restricted by limited knowledge of the contemporary relationships between the vegetation and pollen rain of Neotropical ecosystems, especially for more open vegetation such as savannas. This research aims to improve the interpretation of these records by investigating the vegetation and modern pollen rain of different savanna ecosystems in Bolivia using vegetation inventories, artificial pollen traps and surface lake sediments. Two types of savanna were studied, upland savannas (cerrado), occurring on well drained soils, and seasonally-inundated savannas occurring on seasonally water-logged soils. Quantitative vegetation data are used to identify taxa that are floristically important in the different savanna types and to allow modern pollen/vegetation ratios to be calculated. Artificial pollen traps from the upland savanna site are dominated by Moraceae (35%), Poaceae (30%), Alchornea (6%) and Cecropia (4%). The two seasonally-inundated savanna sites are dominated by Moraceae (37%), Poaceae (20%), Alchornea (8%) and Cecropia (7%), and Moraceae (25%), Cyperaceae (22%), Poaceae (19%) and Cecropia (9%), respectively. The modern pollen rain of seasonally-inundated savannas from surface lake sediments is dominated by Cyperaceae (35%), Poaceae (33%), Moraceae (9%) and Asteraceae (5%). Upland and seasonally-flooded savannas were found to be only subtly distinct from each other palynologically. All sites have a high proportion of Moraceae pollen due to effective wind dispersal of this pollen type from areas of evergreen forest close to the study sites. Modern pollen/vegetation ratios show that many key woody plant taxa are absent/under-represented in the modern pollen rain (e.g., Caryocar and Tabebuia). The lower-than-expected percentages of Poaceae pollen, and the scarcity of savanna indicators, in the modern pollen rain of these ecosystems mean that savannas could potentially be overlooked in fossil pollen records without consideration of the full pollen spectrum available.